Rotating shafts and rotors are utilized in many machines, including motors, generators, and turbines to efficiently transmit kinetic energy between components within or external to the machine. Typically, the rotors associated with a machine rotate about an axis relative to a stationary frame of reference. The stationary frame of reference may be defined as the non-rotating part machine. In some cases, particularly in electrical motors and generators, an electrical connection must be made between the stationary part of the machine and the rotating part of the machine. Direct current electrical motors and generators, for example, utilize brushes to electrically connect and commutate stationary current sources or sinks with electrical windings on the rotor.
Slip rings are also utilized for establishing a connection to a rotor. A slip ring consists of a conductive circle or band mounted on a rotor, but electrically insulated from the rotor and other slip rings. Electrical connections from components on the rotor may be connected to the slip rings, and stationary contacts or brushes can rub against rings to transfer electrical power or signals to and from the stationary part of the machine.
In certain machines, however, slip rings, brushes, and mechanical contacts can wear out, and they may not be practical in terms of durability and reliability. Furthermore, rubbing mechanical contacts against a slip ring may effectively degrade signals and may induce unwanted noise and/or impose limits in the signal bandwidth such that communications between the rotor and stationary part of the machine is compromised.
To overcome such limitations, rotary antenna systems have been proposed for providing non-contact electrical communications (telemetry) between a rotating and stationary part of a machine. Rotary antennas typically consist of a pair of circular “hoop”-shaped and concentrically aligned antennas: one attached to the rotating part, and one attached to the stationary part of the machine. The rotating antenna and the stationary typically must be carefully aligned both axially and radially with a minimum air gap separation for suitable coupling between antennas. Therefore, heavy and complex support structures are typically utilized to mount the stationary antenna to the stationary part of the machine. Manual alignment of the stationary antenna with respect to the rotating antenna is often a time consuming and tedious task, requiring multi-dimensional adjustments of the stationary antenna. Furthermore, if the rotor translates with respect to the stationary frame (due to expansion, contraction, or other factors), the antennas may become misaligned during operation and communications and or inductive power transfer between the antennas may be interrupted.
Therefore, a need remains for improved systems and methods for a translating telemetry stationary antenna.